This invention relates generally to optical couplers. More particularly, this invention relates to an adjustable adapter for coupling a film or video camera to an optical viewing device such as an endoscope, borescope or the like, so that images viewed by the optical scope can be filmed or photographed.
Previous devices for coupling a camera with an endoscope, arthroscope, borescope or similar viewing apparatus have been subject to commonly encountered problems which have limited their effectiveness. For example, when the coupled borescope and camera arrangement is used in a liquid (moist) environment, prior couplers commonly are unable to prevent minute liquid quantities from seeping in between the borescope eyepiece and the coupler. This liquid becomes entrapped and tends to fog the optics of the coupled arrangement.
Another common problem found in prior couplers or adapters arises when the optical scope is rotated relative to the coupler in order to vary the orientation of the optical scope with respect to the camera. In this instance, a coupling ring associated with the adapter, which engages the scope eyepiece, tends to bind up or present varied resistance during rotation, instead of providing a smooth and steady rotational adjustment.
Exemplary attempts to provide improved coupling devices or adapters are illustrated in U.S. Pat. Nos. 4,611,888; 4,413,278 and 4,264,16. Such coupling devices have been found to include several key limitations which thus far have not been effectively eliminated. One of these shortcomings arises because it is standard practice to use an adapter to couple an optical scope to a camera without first removing the scope's eyepiece optics. The disadvantage of coupling with the scope's eyepiece optics stems from the fact that the eyepiece optics provide a virtual image to the attached camera rather than the real image. The eyepiece optics are designed for visual use by a human eye which can generally resolve only about 8 to 10 lines/mm. While such a virtual image is acceptable for this low level of resolution, such is considered unacceptable for photography with modern cameras. A virtual image from the scope's eyepiece optics does not allow the user to achieve the high resolution benefits which a camera could provide if it received the real image from the optical scope (by bypassing the eyepiece optices), rather than the virtual image. In contrast to the 8 to 10 lines/mm ordinarily resolved by a human eye, a video camera can resolve between 40 and 60 line pairs/mm and, depending on the type of film, and a film camera can provide an even higher level of resolution. Thus, a coupling limitation exists in prior devices whereby the camera cannot achieve a desired high resolution level because of optical degradation and light loss occurring in the image as it passes through the optical scope's eyepiece optics.
Another limitation common in prior coupling devices is that a user of the coupled arrangement is unable to insert an auxiliary lens between the optical scope and the camera while they remain coupled together. An adapter which facilitates the use of auxiliary lenses or filters in a quick and easy fashion is essential when it is necessary to produce films or photographs having certain special effects. Prior adapters which contain no provision for auxiliary lens usage require uncoupling of the borescope or camera from the adapter so that shutter attachments or the like, providing auxiliary lenses, can be inserted between the camera and the optical scope. Often, when the photographer is trying to capture a rapidly changing microscopic image using a borescope, there is not enough time available for such uncoupling to allow for the attachment and detachment of auxiliary shutters or lens devices as needed.
Yet another constraint on the effectiveness of prior coupling adapters can be found in devices which utilize a relay lens to direct the image viewed by the optical scope to the camera lens. A relay lens is sometimes provided which consists of a single optical piece or in which the relay lens is not adjustably positionable in a manner providing focus control. In either of these arrangements, optimum optical efficiency is not possible. Greater efficiency in a relay lens arrangement can be obtained if the adapter utilizes a relay lens having multiple optical pieces for improved enlargement of a relayed image to a size appropriate for the camera. Optical efficiency and image quality can be further improved if the adapter can be provided with an adjustably positionable, multi-element relay lens assembly which allows for enhanced focusing control.
There exists, therefore, a significant need for a coupling adapter which can be utilized with an optical scope having its eyepiece optics removed, thus allowing the attached camera to receive an improved image having a high degree of resolution. Additionally, an improved adapter is needed which can provide selective orientation of the optical scope relative to the camera, which allows for the utilization of auxiliary lenses without requiring uncoupling or additional attachments, and which provides improved focusing control, optical efficiency and image quality through the use of an adjustably positionable, multi-element relay lens. Moreover, an improvement is needed wherein a borescope or the like, and a camera are coupled together in a manner facilitating detection of a real image by the camera directly at the camera aperture. The present invention fulfills these needs and provides further related advantages.